Irritable bowel syndrome, or IBS, is an intestinal condition that affects up to 15 percent of the U.S. population. IBS typically begins in your teens or early 20s and causes intermittent bouts of abdominal pain and altered bowel movements. One of the hallmarks of IBS is the lack of an obvious mechanical, inflammatory or biochemical explanation for your complaints. The exact cause of IBS is unknown, so treatment usually focuses on dealing with its symptoms. Although antihistamines are not currently used for treating IBS, data emerging from clinical studies suggests that intestinal histamine receptors could play a role in triggering IBS, and certain antihistamines may reduce IBS symptoms.
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IBS symptoms include abdominal discomfort or pain, bloating, a change in the consistency or frequency of your bowel movements, mucus in your stool and a sense of incomplete emptying following bowel movements. Although one bowel pattern usually predominates, some patients alternate between constipation and diarrhea. Symptoms are often triggered by specific foods or stress and are typically relieved following a bowel movement. The possible mechanisms underlying IBS symptoms are legion, but enhanced intestinal sensitivity to substances normally produced in your body -- serotonin, prostaglandins, hormones, growth factors or histamine -- is one likely candidate.
Your intestinal activity is influenced by mechanical signals generated by stretching of its walls, electrical signals arriving from your nervous system, and chemical signals initiated by substances, such as histamine, coursing through your bloodstream. Histamine attaches to cellular receptors that control several aspects of bowel function, including motility, absorptive capacity and permeability, or “leakiness.” If your histamine receptors are unusually sensitive, which appears to be the case in some IBS patients, your intestines' response to histamine is increased. Presumably, blocking these hypersensitive cellular receptors would alleviate IBS symptoms. This is in fact the basis for several currently available treatments for IBS, which are aimed at blocking serotonin receptors. Antihistamines may one day prove useful, too, but not all antihistamines are equally effective at blocking intestinal histamine receptors.
In 2010, scientists at Tohoku University Graduate School of Medicine in Sendai, Japan, demonstrated that patients with IBS exhibited exaggerated histamine activity in their lower intestines when compared to control subjects, and a study published in the September 2010 issue of “Gut” demonstrated that ketotifen, a mast cell-stabilizing antihistamine, decreased symptoms and improved quality-of-life measurements in 60 patients with IBS. However, the researchers could not identify the specific mechanism for antihistamines’ effects in IBS patients.
Considerations and Precaution
The underlying cause of irritable bowel syndrome has not been identified. Patients with IBS respond variably to different classes of medications and lifestyle changes, so the mechanisms contributing to your IBS symptoms could differ from another person’s. Preliminary research suggests that antihistamines might provide relief to some IBS patients, but it is not yet clear why or how. It is also far too early to determine which antihistamines might prove useful for treating this troubling disorder. Like all medications, antihistamines carry their own burden of side effects, so ask your doctor before you try any new approaches to your IBS.